This invention relates to door latches and more particularly to a cinching door latch for an automotive vehicle.
An automotive door latch typically includes a fork bolt that is pivoted between an unlatched position and a primary latched position when the door is closed to latch the door in the closed position. The fork bolt is typically held in the primary latched position by a detent lever that pivots between an engaged position and a disengaged position. The detent lever holds the fork bolt in the primary latched position when in the engaged position and releases the fork bolt when in the disengaged position so that the door can be opened.
The fork bolt is pivoted to the primary latched position by a striker attached to the door jamb when the door is closed. In some instances, the door may not be closed with enough force to pivot the fork bolt all the way to the primary latched position where the fork bolt is engaged and held in the primary latched position by the detent engaging a primary latch shoulder of the fork bolt. Consequently the fork bolt includes a secondary latch shoulder that is easily engaged by the detent lever to avoid any possibility of the door opening when the vehicle is moving down the road. This is known as the secondary latch position. It is also known to provide a cinching door latch in which the fork bolt is driven to the primary latched position once the door has been closed with enough force so that the fork bolt is pivoted to the secondary latch position where the secondary latch shoulder of the fork bolt is engaged by the detent lever. Alternatively, the cinching mechanism can be actuated when the fork bolt is pivoted toward the primary latched position a predetermined distance even if the secondary latch shoulder is not engaged.
This invention provides an automotive door latch that has a cinching mechanism for assuring that the fork bolt is in a primary latched position when the door is closed. The cinching mechanism of the invention has a cinching gear drivingly connected to the fork bolt, a power driven planetary gear set for driving the cinching gear, and a one-way device for limiting rotation of an element of the planetary gear set to one direction so that the fork bolt can be latched in the primary latched position manually without the necessity of back driving the input to the planetary gear set in the event of power failure. The cinching mechanism also preferably includes a release mechanism to disable the one-way device so that the fork bolt can move to an unlatched position without back driving the input to the planetary gear set.